Embodiments of the present invention relate generally to medical imaging systems, and more particularly, to ultrasound imaging systems, especially for cardiac imaging.
Cardiac remodeling (CR), also referred to a ventricular remodeling, is the change in the size, shape and/or function of the heart, which can occur after injury to the left ventricle. The injury most commonly results from acute myocardial infarction (AMI), which is usually transmural, and evidenced as ST segment elevation in the ECG waveform. However, AMI generally causes regional decrease of myocardial function in the region suffering from lack of blood supply, which results in increased work demand from the remaining regions of the heart.
CR is a process that involves changes of the myocardial tissue properties (e.g. contractility) and is accompanied by an increase in the myocardial mass and in particular left ventricular (LV) mass and volume, as well as a change in the shape of the ventricle that eventually leads to congestive heart failure (CHF). Thus, as more people survive AMI, more people are potentially at risk of CHF. Post-AMI remodeling is asymmetric and is initially triggered and associated with infarct expansion. Infarct expansion, which is related to work performed by myocytes that do not receive enough blood supply (ischemic), occurs mostly through apoptosis (programmed cell death).
Known clinical practices to determine remodeling indices are based on serial follow-ups to measure global functional parameters, for example, ejection fraction and LV volumes. The follow-up and monitoring of these indices are commonly used as indices of success of a particular therapy (e.g., administered medications). These global indices are, however, of low sensitivity. Specifically, these indices are of very low sensitivity to cardiac changes occurring post-AMI, and to regional changes, which actually initiate the cascade of events eventually leading to heart failure.
One known system for assessing cardiac remodeling uses cardiac tagged-MRI. However, the system is extremely expensive and of limited availability. In ultrasound imaging, there are no quantitative measures of regional myocardial function (even among those based on echo-ultrasound speckle tracking). Current clinical ultrasound methods only allow quantification of the function of the whole 2D/3D volume of the myocardium. Additionally, no quantitative ultrasound measures of myocardial remodeling exist. Accordingly, there is no efficient indication that may guide a cardiologist with respect to how to slow or reverse the remodeling process.